PTA 10-排序6 Sort with Swap(0, i) (25分)
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题目地址
https://pta.patest.cn/pta/test/16/exam/4/question/678
5-16 Sort with Swap(0, i) (25分)
Given any permutation of the numbers {0, 1, 2,..., N-1N?1}, it is easy to sort them in increasing order. But what if Swap(0, *)
is the ONLY operation that is allowed to use? For example, to sort {4, 0, 2, 1, 3} we may apply the swap operations in the following way:
Swap(0, 1) => {4, 1, 2, 0, 3}
Swap(0, 3) => {4, 1, 2, 3, 0}
Swap(0, 4) => {0, 1, 2, 3, 4}
Now you are asked to find the minimum number of swaps need to sort the given permutation of the first NN nonnegative integers.
Input Specification:
Each input file contains one test case, which gives a positive NN (\le 10^5≤10?5??) followed by a permutation sequence of {0, 1, ..., N-1N?1}. All the numbers in a line are separated by a space.
Output Specification:
For each case, simply print in a line the minimum number of swaps need to sort the given permutation.
Sample Input:
10
3 5 7 2 6 4 9 0 8 1
Sample Output:
9
/* 评测结果 时间 结果 得分 题目 编译器 用时(ms) 内存(MB) 用户 2017-07-07 11:35 答案正确 25 5-16 g++ 24 2 测试点结果 测试点 结果 得分/满分 用时(ms) 内存(MB) 测试点1 答案正确 15/15 2 1 测试点2 答案正确 3/3 24 2 测试点3 答案正确 3/3 12 1 测试点4 答案正确 2/2 2 1 测试点5 答案正确 1/1 2 1 测试点6 答案正确 1/1 2 1 有点技巧性的题目,mooc上讲了,主要是找排序的环。有0环的交换次数为n-1,无零环为n+1 建了三个数组,A是存数,B是存i号元素放在了哪个位置,Checked是放这个元素有没有被访问过。 坑:必须加一个全局变量做搜索函数起点的备忘录用,否则搜索函数反复调用会导致超时 */ #include<stdio.h> #define MAXN 100000 int A[MAXN],B[MAXN],Checked[MAXN]; int gFindBeginPosition=0; int FindUnchecked(int N) { int i; for(i=gFindBeginPosition;i<N;i++) { if(!Checked[i]) return gFindBeginPosition=i; } return -1; } int main() { int i,N,p,sum; int ringCount=0; int nCount=0; int zeroInPosition=0; scanf("%d",&N); for(i=0;i<N;i++) { scanf("%d",&A[i]); B[A[i]]=i; } if(A[0]==0) zeroInPosition=0; else zeroInPosition=-2; while((p=FindUnchecked(N))+1) { Checked[p]=1; if(A[p]!=p) nCount++; else continue; while(!Checked[B[p]]) { p=B[p]; Checked[p]=1; nCount++; } ringCount++; } sum=nCount+ringCount+zeroInPosition; printf("%d",sum); }
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